# Measure gravity

By the end of this section, you'll learn that:

```
Gravity = Change in Weighted Commitment / # of Members
```

To get there, let's take the gravity calculation one step at a time, starting with each
individual member.

## Moving along the commitment curve

Each community member moves up and down a [commitment curve](../love) at
their own pace. Time is the curve's x-axis and involvement is the y-axis. As
members move along, their [orbit level](../love/orbit-levels) changes.

In the Orbit Model, there are 4
levels with 3 steps each, for a total of 12 levels.

Members progress thru the levels in two ways:

- by achieving new commitment milestones, like progressing from forum observer to active responder to hosting meetups
- by increasing their presence, like progressing from casual observer to someone who is active in the community 5 days per week

![Commitment curve](../commitment-curve.jpg)

☝️ The movement between these levels forms the basis for gravity.

Gravity is a community-level metric, but first we'll look at an individual's participation, then build up from there.

Here's an
example of a how a single member's commitment level changes over time.

| Member | Month         | Commitment | Activity                   | Orbit Level      |
| ------ | ------------- | ---------- | -------------------------- | ---------------- |
| Alex   | January 2022  | 2          | Read newsletter            | Exploring II     |
| Alex   | February 2022 | 5          | Came to an event           | Participating II |
| Alex   | March 2022    | 7          | Was active for 5 days/week | Contributing III |

Between December and March, Alex's commitment has changed by `+4`. During each
month that Alex's commitment increased, she reached a new milestone in terms of
the commitment level and frequency of her activities.

## Comparing change between orbit levels

Now imagine that we added up the commitment change for every member in the
community. That's what we'll do next.

Quick note: in the examples below, we'll use just the 4 orbit levels, rather than the the
orbit levels + steps. This is to keep the example simple, but 12 steps will
yield fine-grained results in practice.

In this table, each value represents the number of members in that orbit level
during the given month.

| Orbit Level   | January 2022 | February 2022 | March 2022 |
| ------------- | ------------ | ------------- | ---------- |
| Exploring     | 17           | 15            | 12         |
| Participating | 8            | 9             | 10         |
| Contributing  | 4            | 5             | 6          |
| Leading       | 1            | 1             | 2          |

Our example community has undergone some changes in the last 3 months. There's 1
new leader, 2 new contributors, and 2 new participants. We have also 5 fewer
explorers, but that's okay thing since they've moved up to other levels.

### Weighted commitment

Okay, now we know how our members have moved through the different levels, but in reality, all levels aren't created equal. Getting an explorer to participate is great, but getting a member to step up and become a leader is both valuable and difficult. It requires _much_ more commitment.

If we were to stop here, we'd have some interesting information, but that info would not reflect the dedication nor difficulty required for moving members up the commitment curve.

This is where weights come in. **Weighting provides more "credit" for moving members to higher and higher levels of commitment**.

This table shows the # of members in each orbit level in January 2022, multiplied by
the weight associated with each orbit level, squared. Why squared? Moving a member from
Orbit 2 to 1 is a much larger achievement per member from 4 to 3. Metaphorically, the
community has to pull harder and longer for it to happen.

```
Weighted Commitment(Level) = Weight(Level) ^ 2 * # of Members
```

| Orbit Level   | Weight | # Members | Weighted Commitment |
| ------------- | ------ | --------- | ------------------- |
| Exploring     | 1      | 17        | 1^2 \* 17 = 17      |
| Participating | 4      | 8         | 4^2 \* 8 = 128      |
| Contributing  | 7      | 4         | 7^2 \* 4 = 196      |
| Leading       | 10     | 1         | 10^2 \* 1 = 100     |
| Total         |        | 30        | 441                 |

Let's compare the weighted commitment scores between January, February, and March.

| Orbit Level   | January 2022 | February 2022 | March 2022 |
| ------------- | ------------ | ------------- | ---------- |
| Exploring     | 17           | 15            | 12         |
| Participating | 128          | 144           | 160        |
| Contributing  | 196          | 245           | 294        |
| Leading       | 100          | 100           | 200        |
| Total         | 441          | 504           | 666        |

The weighted commitment between January and February changed by `+63`, or `+2.1 per member`. The weighted commitment between February and March changed by
`+162`, or `+5.4 per member`.

```
Gravity = Change in Weighted Commitment / # of Members
```

The numbers `+2.1` and `+5.4` are our community's gravity for January and
February respectively. February's gravity is that much higher because the
community was able to "pull" one member from being a contributor to a leader.

The way to read the gravity number is that, on average, the community increased
each member's weighted commitment by the calculated amount, where weighted
commitment = the weight of their orbit level, squared.

## Find bottlenecks using orbit levels

To find bottlenecks in your community's field of gravity, you can look at
the percentages of members who move up and down month over month. Here's an
example of a table that compares data from two months.

**Period: March to April 2022**

| Orbit Level | Moved up | Held | Moved down |
| ----------- | -------- | ---- | ---------- |
| 4           | 25%      | 55%  |            |
| 3           | 18%      | 61%  | 21%        |
| 2           | 12%      | 74%  | 14%        |
| 1           |          | 82%  | 18%        |

Members get stuck at levels with a low "Moved up" percentage. Levels with a high
"Moved down" percentage struggle to keep members engaged at that level. It's
good to keep an eye on these numbers to see how they change over time. If 25% of
members moved up from Orbit 4 in one month and the next month only 10% did,
investigate to see what happened.

For more granularity, this analysis can be done with steps in addition to the
orbit levels.

## Increasing gravity

There are two levers for increasing the gravity of a community: love and reach. Tactically, this looks like providing more relevant opportunities for members to get involved, and creating more opportunities for members to connect with one another.

To increase love, consider programs that enable:

- higher commitment activities
- more frequent activities

To increase reach, try tactics that:

- create more opportunity for member-to-member connections
- gain outside influence

See the [love](../love) and [reach](../reach) pages to learn more.
